The present invention relates to an exhaust gas cleaning device for eliminating particulates such as carbon particles in exhaust gases of an internal combustion engine, particularly to an exhaust gas cleaning device provided with at least one particulates collecting member and heating means for burning the particulates collected by the particulates collecting member.
One of the conventional exhaust gas cleaning devices for an internal combustion engine, comprises a filter member operating as the particulates collecting member for collecting particulates mainly composed of carbon particles, which is disposed in an exhaust gas flowing passage. In this conventional device, the particulates collected by the filter member are heated by the exhaust gases flowing from the internal combustion engine to be burnt off.
However, this conventional device has the problem that the filter member is clogged with the collected particulates.
Namely, the temperature of the exhaust gases does not rise above the combustion temperature of carbon (about 600.degree. C.) under the usual driving condition of a vehicle running on a street.
Therefore, the collected particulates do not burn to clog the filter member.
In order to prevent the filter member from being clogged with the collected particulates, it has been proposed that the device further comprises heating means which is positioned on the upstream side of the filter member adjacent thereto for burning the collected particulates when the amount thereof increases,
However, such a device as described above has the problem that a sufficiently large amount of heat required to burn the collected particulates completely, cannot be obtained.
Namely, the upstream side of the filter member can be heated to the combustion temperature of the collected particulates by a relatively small amount of heat. But in order to heat the whole of the filter member to the above described temperature, a considerable large amount of heat is required.
In addition, since a large amount of exhaust gases, of which the temperature is lower than that of the heating means, flow through the filter member while the filter member is heated by the heating means, heating efficiency is lowered.
Accordingly, one object of the present invention is to provide an exhaust gas cleaning device wherein heating efficiency of the particulates collecting member is improved.
Another object of the present invention is to provide an exhaust gas cleaning device wherein at first one portion of the particulates collecting member is rapidly heated by means of the heating means and then the other portion thereof receives heat from the heated portion thereof.
Still another object of the present invention is to provide an exhaust gas cleaning device provided with such means to stop the flow of exhaust gases or reduce the amount of the exhaust gases flowing through the particulates collecting member while the particulates collecting member is heated by means of the heating means.
A further object of the present invention is to provide an exhaust gas cleaning device comprising heating means which is operable under driving conditions wherein the amount of flowing exhaust gases is small.